1. Field of the Invention
The invention relates to earth working and specifically to agricultural tilling apparatus having counter-rotating digger shafts carried on a centrally tiltable frame with the diggers being adapted to till sandy soils while leaving an untilled ridge between furrows.
2. Description of the Prior Art
Cultivators are generally adapted to do a substantially complete job of breaking-up soil clumps throughout the width of the cultivator apparatus, whereby the soil is fully prepared to receive seeds at any desired location in the pulverized path created by passage of the apparatus. An example is provided by the small garden cultivator described in U.S. Pat. No. 3,773,112 to Zinck, which apparatus employs a pair of parallel shafts each carrying a plurality of digger blades or hoeing tools, said shafts being powered to rotate in respectively opposite directions. A commercial embodiment of this patented device has been observed to break-up the soil to an extreme degree.
On a larger scale, farm equipment has been proposed in Swiss Pat. No. 132,236 to Grunder & Co. for a tractor driven apparatus employing counter-rotating digger shafts having the diggers on the rear shaft spaced between the diggers on the front shaft, with the digger spacings suggesting that the soil is again thoroughly broken-up. Another apparatus having counter-rotating shafts is taught in U.S. Pat. No. 1,333,543 to Greene, wherein the shafts are carried on a self-propelled cart.
Although the noted devices are capable of adequately tilling soil, in some applications it is desirable to leave a portion of the soil untilled, such as the soil between the seed rows. Especially in areas having sandy soil or adobe-like soil, wind erosion creates a major problem if the soil is over-cultivated. Often these types of soil achieve stability when not disturbed by a tiller, and thus, wind does not erode the ground in untilled areas as badly as in tilled areas. The conventional philosophy of tilling the entire width of soil in the path of the tiller therefore is a detriment when sandy or adobe-like soils are encountered in windy areas.
A further unanswered need in the cultivation of such soils especially prone to wind erosion is the ability to quickly adjust the depth of tiller blades as the tilling machine is traversing the fields. Because cultivation should be minimized to prevent loose soils, tiller blades may advantageously be carried in such a manner that their digging depth is substantially instantaneously adjusted as the tiller crosses high or low points in a field. If the tiller blades are carried on a cart with front and rear wheels, the blades can easily dig too deeply into the soil at a sudden rise in the field, while depth cannot be efficiently controlled if the digger shafts have no supporting wheels at all.
A further problem with sandy soil is that it tends to have very little cohesiveness immediately after being tilled. The conventionally proposed digger blade resembles a curved, pointed rod or a curved knife, adapted to enter and break cohesive soils. In sandy soil, the path created by such a relatively narrow, sharp blade is itself very narrow both because of the narrow blade width and because the sandy soil may fall back into the furrow. In sandy areas, the conventional tiller blade may therefore be inadequate to create a furrow having a wind resistant design. A broader blade creates another possible problem by raising a great deal of dust that may contaminate the tiller motor.
The present invention seeks to create a tiller for sandy soils that solves all of the above problems.